Machine tool



Feb. 24,1948. POLK ETAL 2,433,527

MACHINE TOOL Filed Aug. 21, 1944 3 Sheets-Sheet 1 Feb. 24, 1948. L. F. POLK ETAL 2,436,527

MACHINE TOOL Filed Aug. 21, 1944 p 3 Sheets-Sheet 2 Z 49 4 mg 4 1 47 I 43 s figs/10K;

BY 107W 'L. F. POLK ETAL Feb. 24', 1948.-

MACHINB TOOL Filed Aug. 21, 1944 3 Sheets-Sheet 3 Patented Feb. 24, 1948 MACHINE TOOL Louis F. Polk and Willis Fay 'Aller, Dayton, Ohio, assignors to The Sheffield Corporation, Dayton, Ohio, a corporation of Ohio Application August 21, 1944, Serial No. 550,879

This invention relates to surfacing or truing the operative surface of a grinding wheel.

One object of the invention is the provision of a self-contained unit adapted to be fixed on the reciprocable table of surface grinders, and including a base, a crusher wheel mount and a power drive for the crusher wheel so that the latter can be driven at a comparatively slow speed of rotation when the grinding wheel of the surface grinder and the crusher wheel are brought into crushing engagement one with the other, producing the desired formation on the surface of the grinding wheel.

Another object is the provision of a unitary surface grinder attachment of the character mentioned, in which the base of the unit is also provided with a work holder arranged in alignment with the plane of rotation of the crusher wheel.

Another object is the provision of a crusher wheel mount so arranged as to automatically move the crusher into the grinding wheel at a controlled rate in which a constant pressure of the crusher wheel-against the grinding wheel is maintained.

Another object is the provision of a rotatable crusher wheel for truing the surface of a grinding wheel, in which the crusher wheel is pivotally carried for bodily movements towards and from the grinding wheel with provision for the automatic movement of the crusher wheel at a 7 controlled rate.

Another object resides in the combination with a surface grinder having a rotatable power operated grinding wheel and a reciprocable table, of a base fixed n the table and reciprocable therewith below the grinding wheel, the base being provided as a unitary attachment which includes a crusher wheel, a motor drive for the crusher wheel and control means for automatically moving the crusher wheel towards the grinding wheel at a controlled rate.

Other objects and advantages of the. invention will be apparent from the following description, the appended claims, and the accompanying drawing, in which,

Fig. 1 is a perspective view of a portion of a surface grinder provided with a unitary attach- 8 Claims. (01. 125-2) the crusher wheel being movably supported and automatically movable towards the grinding wheel;

Fig. 4 is a yertical section on the line 4-4 of Fig. 3;

Fig. 5 is a vertical section on the line 5-5 of Fig. 3:

Fig. 6 is a top plan-view of the crusher and crusher mount;

Fig. 7 is a side elevation showing a modified form of crusher mount and drive unit; and

Fig. 8 is a horizontaksection on the line 8-8 of Fig.- 7.

Referring more particularly. to Figs. 1 and 2 of the drawing, i0 generally designates the supporting structure of a grinding machine having a reciprocable work carrying table II guided for movement on suitable ways and power operated in any conventional manner so as to move longitudinally back and forth through a stroke that can be determined by the operator. Suitable control wheels or levers l2 and 13 may be manually operated to adjust the table laterally or in the direction in which the table reciprocates.

Extending upwardly from the supporting structure i0 is a suitable housing i4 containing a motor preferably in direct connection with a grinding wheel shaft on the end of which is a grinding wheel l5. Suitable bearings, not shown, are

80 provided in the housing It for the grinding wheel shaft. The housing is may be vertically adjusted for movement towards and from the table II by a suitable hand lever I! which turns an adjusting nut cooperating with a vertical carrying screw arranged within the housing M to adjust the vertical height of the grinding wheel.

The table Ii of the surface grinder carries a flat base [9 the lower surface of which rests directly on the flat upper surface of the table. Suitable clamping means 20 serve to hold the base I9 firmly in position on the table. This base the workpiece or workpieces by the grinding wheel i5. Thus the sectional form of the crusher wheel is similar to or exactly complementary to the surface formation to be imparted to the.

grinding wheel l5. When the grinding wheel is brought down into pressure engagement with the crusher wheel 24 and the crusher wheel isslowly rotated, the crusher wheel drives the grinding wheel at substantially the same peripheral speed,

and the grinding wheel is formed or trued by the pressing or crushing action thus produced as several rotations of the grinding wheel take'place. The crusher wheel 24 is preferably made of steel or other suitable hard metal, and may be provided with an annular series of slots 25 the edges of which may give a biting or chipping action on the grinding wheel surface as the grinding wheel and thecrusher wheel are rotated.

The end of the shaft 23 has a detachable flexi- I the operator very slowly feeds the grinding wheel ble connection 21 to a short shaft 28. This flexi ble connection in the particular form illustrated comprises flanged coupling plates one fixed on the end of each shaft, with a yielding strip of rubber or fabric interposed between the plates and with connection screws or bolts 2! coupling the driving and the driven plates together. However, any other suitable connection may be employed.

The shaft 28 is driven by power means so as to bepositively operated at a comparatively low rate of speed. For this purpose the base I9 is provided with an electric motor 30 which is electrically connected preferably through a suitable startin switch carried on the motor, and through a suitable flexible connection lead to any suitable source of power. The shaft of the motor drives speed reducing gearing, shown as a worm gear 3| on the motor shaft 32 and meshing with a work gear 33 on the shaft 28. A speed reducing gear housin 34 encloses the worm and worm wheel drive and provides a bearing for the shaft section 28. The drive connection between the motor and the shaft 28 is such that the shaft is turned at a comparatively low rate of speed of the order of about300 turns per minute where the diameter of the crusher wheel is about three inches to four inches. The surface speed of the crusher should be several hundred feet per minute.

The workpiece or workpieces to be surfaced by the grinding wheel are carried by a holder 36 arranged in alignment with the plane of rotation of the crusher wheel and shown in Fig; 1 as mounted directly on the base l9 at a suitable distance from the crusher wheel mount 2|. Suitable clamp screws 31 serve to hold the work 38 in a trough or work space in the holder 36 so that the surface of the workpiece will be ground to the desired form as the table II reciprocates back and forth under the grinding wheel.

While surfacing the workpieces, the stroke of the table is adjusted to be only slightly in excess of the total length of the work, and as the table reciprocates, the hand lever 11 may be operated to feed the grinding wheel downwardly until the desired form is given to the work. In time the surface of the grinding wheel is worn and requires retruing or resurfacing. When this time arrives, the power drive for the grinding wheel and the power drive by means of which the table I I is reciprocated are disconnected or deenergized and the operator turns the manual feed lever or wheel so that the table is adjusted in the direction of its length until the axisof the grinding wheel is over the axis of the crusher wheel 24. The operator, by turning the hand lever l1, then brings the stationary grinding wheel down into pressure contact with the crusher wheel, and when this is accomplished, he starts the motor 30 so that the crusher wheel will be rotated comparatively slowly, and by reason of its pressure engagement with the grinding wheel it will rotate the grinding wheel at substantially the same peripheral speed-as the crusher wheel. This will downwardly. and after several rotations of the grinding wheel, the number of rotations depending on the extent wear has taken place, the grinding wheel will be restored to its desired and exact form. After the motor I! is d'eenergized, the grinding wheel may be raised' before further grinding of the work takes place although it is preferred that the top of the crusher wheel be arranged exactly level with the top of the work after the work is properly ground so that the same spacing of the grinding wheel from the table is required in the final grinding of the work and the final crushing action of the grinding wheel. Thus the grinding wheel may remain in position after it is properly trued by the crusher and be properly set for grinding withoutchanging its height. Since the crushing wheel 24 is arranged in exact alignment with the work position, no lateral adjustment of the table II is required following the crushing action.

The base ll, the motor 30 with its gear reducing unit, and the crusher and crusher mount are all arranged as a compact unitary assemblage that can be appiied to and removed from existing surface grinders of various types and may be applied to surface grinders of widely varying design without necessitatlngany change in the surface grinder itself. It' may be used when required. and taken off merely by removing or releasing the clamping means 2! if the work and the wheel form are such that 'the'crusher is not needed in any particular surfacing operation.

The unit embodies drive means for the crusher so that the crusher and the grindin wheel 'will be rotated at a'desire'dsiow rate of speed, much slower than the usual'i'grindlng wheel speed oftained from the grlnding'wheel drive with which a surface grinder is ordinarily provided. No addi- 40 tional rovision is necessary in the surface grinder itself for the'ioperationof the grinding wheel at the desiredslow speed in the crushing operation. In this form of arrangement just described, the operator slowly ;turns the down-feed control of the surface grinder, during the crushing operation. so that imdue or breaking strains that might injure the grinding wheel will not be applied by the crusher-I} In the form of construction shown in Figs. 3 to 6 inclusive. the crusher is. automatically movable towards the grinding wheel at a controlled rate, preventing the exertion of too much force on the grinding gwljieel during the crushing operation. In this gbgrstruction, the base i9 is adapted for support the workfcarrying table of the grinding'machine such as the machine a part of which is shown-iii fig. 1. 'lfhegi'inding wheel l5 of the surface'grfnger is adapted to be formed or trued by theygriisher'wheel 4! having the desired surface formation. The holder I! maybe provided with a supportfor the work, as disclosed in connection with the construction shown in Figs. '1 and 2; ii-

The crusher wheel 40 is carriedby a shaft 4| which is arranged forfreei rotation in the two spaced arms if of a crusher wheel mount 43.

a The latter is-pirotally supported by ivot pins provide the desired crushing or truing action, as 76 carrying meanssuoir-as-the :pins ll on' which roundness of the grindin crusher and the crusher mount.

In crushing the grinding wheel, the operator Q moves the crusher wheel, lay-operating the work carrying table. until it indirectly-beneath the grinding wheel, with the power drive for the grinding wheel disconnectedo'r deene'rgized. The

grinding wheel is thenlowered -until its pressure against the crusher wheel causes-the body portionof the wheel mount '43 to-be lifted from the stop screw 50. The extent"to which the wheel mount is moved out of its normal position depends upon the amount of'material to be taken from the surface of the grinding wheel. Ordinarily this may be expressed in thousandths of an inch. The operator then starts rotation of the grinding wheel at a suitable slow speed so that both wheels will rotate with aspeed'of the order of about three hundred feet per minute. In this case, where the grinding; wheel furnishes the power drive, in crushing.-an auxiliary grinding wheel motor may be required if the surface grinder itself is not originally provided with means for operating the grinding wheel at the required low rate of speed.

Before the grinding wheel is rotated, the operator adjusts the weights on=the crusher mount in accordance with the width; bf the wheei ,.the surface formation to be imparted to it,- and themake of the wheel itself, factors which govern the pressure that the wheel can stand without causing breakage or shattering of; the grinding wheel.

With a wider wheel, of course. a greater pressure can be exerted against it than in the case of a grinding wheel that -is comparatively narrow. After the wheels are-rotated, the desired pressure of the crusher wheel is automatically maintained,

by gravity action, until the grinding wheel is sufficiently trued to permit the body portion of the mount 43 to come down i to contact with the stop 50. During the final 011.1%1113 action, any out-ofwheel will-be removed as the crusher wheel mount bottoms on the stop. After the grinding wheel is trued, and the operator notes that the wheel mount is remaining stationary on the stop 50, the-rotation of the grinding wheel is stopped and the work: carrying table is then adjusted to bring the grinding wheel over to the work. It will be noted that the final position of the crusher wheel mount is such as to leave the bottom of the grinding wheel at an exact spacing above the reciprdcable' table of the grinding machine, regardlessihf the amount of material taken off of the grinding wheel, since the crusher itself has substantially no wear in any truing operation. Since the work support carries the work so that the finished ground work surface will be at the same level as theifinal crushing position of the crushing wheel, no up and down adjustment of the grinding wheel will be required by the operator after the crushing opera tion. In a subsequent crushing operation, he will merely move the down-feed sufliciently to lower the grinding wheel an amount corresponding to the amount of material to be removed, in crushing.

operated to maintain a desired pressure against In the form of construction illustrated in Figs. 7 and 8, the crusher wheel I2 is automaticallythe grinding wheel during the crushing operation, and a driving motor is provided as a unit with the the invention, the electric driving motor 53 is supported on a base 54 which can be fixed on the table of the surface grinder. The motor is prowheel. This crusher wheel is fixed on a shaft 5l which is rotatably mounted in the two spaced arms 58 of the wheel mount 59. A pivot pin 60 parallel toand spaced from the shaft 51 provides a fulcrum on a post which is fixed by a bolt or bolts 62 on the base 54. The'pivot pin or shaft 60 thus carries the crusher wheel for bodily movement towards and from the grinding wheel, and the body portion of the wheel mount 59 projects outwardly and normally rests against a stop nut 63 which is adjustably arranged on a threaded stud 64 fixed in the base 54. A lock nut 65 serves to hold the nut 63 in various positions of adjustment. The body portion of the wheel mount 59 is provided with means fo readily attaching weights, and for this purpose holes 66 are provided for holding weight locating pins on which the weights may be arranged.

It would be understood that the operator adlusts the weights applied to the body portion or the wheel mount, in accordance with the width of the grinding wheel, and .the hardness or brittleness of the particular grinding wheel involved so that a safe crushing pressure will be exerted by the crusher wheel during the crusher operation. In this crushing operation, the drive of the grinding wheel is disengaged or deenergized, and the crusher wheel is positively rotated at a suitable low rate of speed, by the power supplied from the motor 53. For this purpose the shaft 58 is pro vided with a gear 61 arranged coaxially with pivot pin 60 so that the axis of the gear 51 will be maintained in a constant position during pivotal adjustment of the crusher wheel itself; The gear 61 meshes with a gear 68 fixed on shaft section 69 which is rotatably supported in one of the arms 58 andin a bearing plate 10. The bearing plate is fixed on the crusher wheel mount 59 by a housing wall II which, together with the bearing plate 10, forms an enclosing chamber in which the gears 61 and 68 are arranged. Theshaft section 69 is aligned with the shaft 51 to which the crusher wheel is fixed, interlocking tongues and grooves being provided in these two shaft portions as indicated at I2 so that the crusher will be positively driven either in a clockwise or a counterclockwise direction as viewed in Fig, '7, as desired.

In the construction illustrated in Figs. '7 and 8, the work holder ,36 illustrated in Fig. 1 may be incorporated to carry the top of the ground work in position level with the top of the crusher wheel. With the arrangement of Figs. 7 and 8 a unitary attachment is provided for use on surface grinding machines of various kinds and types without requiring the alteration of the grinding machine itself. Many surface grinding machines are provided with power drives for the grinding wheels that would operate the grinding wheels at excessively high speed during crushing, and many of In this form of assess? i them also have feed means for raising or lowering the grinding wheel such that tremendous pressures could be exerted .by the grinding wheel on a crusher wheel if the axis of the latter were definitely fixed. And in the diflerent grinding machines of different manufacturers, the amount of pressure that is applied with any known force exerted on the adjusting handle or wheel varies greatly, and is not readily ascertalnable by the operator himself. In accordance with \the construction disclosed in connection with Figs. 7 and 8, however, these disadvantages are avoided, as the operator can determine readily from experience or from instructions just how much pressure should be exerted by the crushing wheel without injuring the grinding wheel. and this pressure is automatically maintained during the crushing operation without relying on manual pressures exerted by the operator in this action. The motor drive unit itself is also arranged to give desired and proper surface speed of rotation to the crusher wheel. The crusher unit may, therefore, very readily be used by men without substantial experience in the crushing of grinding wheels, and within a minimum of instruction.

While the forms of construction herein illustrated and described constitute preferred. en bodiments of the invention, it is to be understood that various modifications and adaptations of the invention may be made within the spirit an scope of the appended claims. v v

What is claimed is: 1. A self-contained crusher wheel and drive ,unit adapted to be fixed on the reciprocable work table f a surface grinder for operation back and forth with the work in a plane directly below .the grinding wheel of the surface grinder, said unit comprising a base having a wheel mount, a crusher wheel rotatably supported on said mount and having a surface form similar to that to be imparted to the grinding wheel of the surface grinder, an electric motor carried by said base, and a positive speed reducing drive connection between said motor and said crusher wheel.

2. A self-contained unit adapted to be fixed on the reciprocable work table of a surface grinder for operation back and forth with the work in a plane directly below the grinding wheel of the surface grinder, said unit comprising a base having a wheel mountfa crusher wheel rotatably supported on said mount and having a surface form similar to that to be imparted to the grinding wheel of the surface grinder, an electric motor carried by said base, a positive speed reducing drive connection between said motor and said crusher wheel for driving said wheel at a surface speed of the order ofv 300 feet per minute, and

means for automatically varying the distance between the grin ng wheel axis and the crusher axis during the crushing operation to maintain the crusher wheel in crushing engagement with the grinding wheel.

3. A self-contained crusher wheel and drive i unit adapted to be fixed on the reciprocable table 8 radially towards the grinding wheel to a predetermined position.

4. In combination, a surface grinder having a rotatable grinding wheel, a reciprocable work carrying table, power means for rotating said wheel and means for' feeding said wheel towards and from the table, a base fixed on said table, said base having a wheel mount, a crusher wheel rotatably supported on said mount with a surface form similar to that to be imparted to the grinding wheel, an electric motor carried by said base, and a positive speed reducing drive between said motor and said crusher wheel,

,5. In combination, a grinding machine havin a rotatable grinding wheel, a work supporting table, a rotatable forming crusher wheel for truing the grinding wheel to a predetermined peripheral shape, holding means carried by said work supporting table, a crusher wheel mount movably supported on said holding means for movement towards and from the grinding wheel axis, means for automatically maintaining a constant pressure of engagement between the crusher wheel and. the grinding wheel, means for stopping the crusher wheel movements at a predetermined position, and means for positively rotating said "crusher wheel at a peripheral speed of the order of 300 feet per minute.

6. In combination, a rotatable crusher wheel adapted to true or form a rotatable grinding wheel, a base, a lever pivotally supported on said base and having means rotatably supporting said crusher wheel, said lever supporting said crusher wheel for bodily movement towards-and from the grinding wheel, stop means for limiting the bodily movement of the crusher wheel towards the grinding wheel, a motor carried by said base and having a speed reducing driveconnection to said crusher wheel for operating the crusher wheel at the speed of the order of 300 feet per minute, and means for maintaining a constant pressure of the crusher wheel against the grinding wheel during the rotation of said wheels,

7. A self-contained crusher wheel unit adapted to be fixed on the reciprocable table of a surface grinder for operation back and forth with the work in a plane directly below the grinding wheel,

said unitcomprising a holder adapted for fixed positioning on the surface grinder table, a crusher wheel carrying bar rotatably supporting a crusher wheel, means pivotally supporting said bar on said holder for vertical bodily movement of the crusher wheel towards the grinding wheel of the surface grinder, means for constantly urging said bar under constant pressure to hold the crusher wheel yieldingly against the grinding wheel, means for controlling the limit of travel of the crusher wheel towards the grinding wheel, and an electric motor carried as a part of said unit and having a speed reducing driving connection to the crusher wheel for positively rotating the crusher wheel.

8. A self-contained crusher wheel unit adapted to be fixed on the reciprocable table of a surface grinder for operation ba k and forth with the work in a plane directly below the grinding wheel, said unit comprising a holder adapted for fixed positioning on the surface grinder table, a crusher wheel mount rotatably supporting a crusher wheel, a shaft spaced from the crusher wheel axis and pivotally supporting saidmount on said holder for bodily movement of the crusher wheel towards the grinding wheel of the surface grinder, a gear fixed to said crusher wheel, a gear meshing with said first gear'and coaxial with to the crusher wheel for positively rotating the 1 268 624 g gi I crusher wheel, said mount having a weight por- 1373833 Robe; Apr 1921 tion overhanging the axis of said shaft to apply 5 1'513758 Hanson 1924 a constant pressure of the crusher wheel against 1536398 Kemp a 1925 the grinding wheel, and adjustable means con-' 1896'533 vumeugie'r Feb 1933 trollable to adjust the limit of travel of the crusher .1'995:3o4 Hanam 1935 "heel wards the W wheeh 10 2,088,084 Gould July 27, 1937 LOUIS F. POLK. 2,100,954 Gould et 'al. Nov. 30, 1937 WILLIS FAY ALLER. FOREIGN PATENTS Number Country 1 Date 1 REFERENCES CITED- 1 183,614 GreatBritain Aug. 3, 1922 The following references are or record in the 15 514,221 Germany Dec. 9, 1930 said shaft, an electric motor carried by said holder UNITED STATES PATENTS and having a speed reducing driving connection Number flle of this patent: 634,473 Germany Aug. 28, 1936 

